Enable SILENT_RULES in SPHINX build
This patch will make builds much less verbose and more verbose at the same time according to SILENT_RULE settings (--enable/disable-silent-rules or make V=0/V=1), see:
$ make clean all html
rm -rf .libs _libs
rm -rf ./_build
rm -f man/*.1 man/*.5 man/*.8
rm -f *.lo
GEN man/knot.conf.5
GEN man/knotc.8
GEN man/knotd.8
GEN man/kdig.1
GEN man/khost.1
GEN man/knsupdate.1
GEN man/knot1to2.1
GEN man/knsec3hash.1
GEN man/keymgr.8
SPHINX html-local